The meniscus is a piece of cartilage located within the knee joint, between the top of the tibia and the bottom of the femur. The meniscus serves to facilitate stable movement of the tibia and femur relative to one another, and to absorb shock and to spread load.
The meniscus is frequently damaged (e.g., torn) as the result of injury and/or accident. A damaged meniscus can impede proper motion of the knee joint and cause pain, among other problems.
More particularly, the essential role of an intact meniscus, and its importance for proper knee function, has been well documented and accepted by the general orthopedic community. An intact and functioning meniscus is critical to optimally distribute weightbearing forces that transfer through the knee joint while maintaining knee stability. The meniscus is also vital to preserving the articular cartilage surfaces of the knee. Loss of meniscal tissue is considered to be a key precursor to the development of knee osteoarthritis.
A major challenge in repairing a torn meniscus is the fact that the tissue itself is a fibrous structure that is not uniformly vascular. The vascular zones of the meniscus comprise about one third of the meniscus tissue and are generally recognized as the “red-red” and “red-white” zones. The red-red zone (i.e., the most highly vascularized portion of the meniscus) is an area in which meniscal repairs are known to heal easily and is located along its outer periphery. The red-white zone extends from the most vascular area towards the inner portions of the meniscus where the blood supply eventually declines to non-vascular tissue (which is sometimes referred to as the “white-white” zone). It is believed that proper surgical technique is of great importance if a successful repair is to be achieved in the red-white zone. It is generally accepted knowledge that about 15% of all meniscal tears occur in the red-red zone, another 15% of meniscal tears occur in the red-white zone, and the remaining 70% of meniscal tears occur in the white-white (or non-vascularized) zone of the meniscus.
Another significant challenge in repairing a torn meniscus is that the size and shape of the tears vary, making the reduction and apposition of the torn tissue difficult to accomplish. Without proper apposition and stability, torn meniscal tissue will not heal properly.
The art of repairing torn meniscal tissue was first developed and pioneered throughout the 1980's by early sports medicine-focused surgeons. The earliest methods employed only suture in the repair. The techniques of “inside-out” and “outside-in” suturing became the so-called “gold standard” for the repair of meniscal tissue. Both of these techniques focused on passing small diameter suture (size 2-0 or 3-0) through the meniscus, reducing and closing the tear, and then tying a suture knot over the knee capsule so as to fixate and stabilize the tear. A feature of these early all-suture repairs was that the surface of the meniscus was kept relatively smooth since the suture knot was outside of the knee joint, and the use of a needle and suture allowed the surgeon a great deal of flexibility in adequately reducing and stabilizing the tear. Eventually, these early surgeons began concomitant use of complementary techniques to promote a vascular response in the more non-vascular areas of the meniscus. Methods such as tear edge and meniscapsular rasping, the application of an interpositional blood clot, trephination to create a vascular channel, and fascial sheath or synovial flap coverage have been shown in several studies to be 150% more effective in healing a torn meniscus when compared to repairs that do not use such concomitant techniques.
The specific issues and challenges associated with the aforementioned all-suture inside-out and outside-in repair techniques are centered primarily on issues relating to the “user interface” and to the “tethering” of the meniscus to the knee capsule. More particularly, the “user interface” issues generally relate to the technical demands required in the operating room: the skill of the surgeon and the number of assistants required to safely pass the needle and suture from the anterior portion of the meniscus through the posterior portion of the meniscus and exit out through the posterior/medial aspect of the knee joint (i.e., the so-called “inside-out” technique); or the passing of a needle and suture from the medial aspect of the exterior of the knee into the knee joint, through the meniscus, the retrieval and re-insertion back into the meniscus, and then passage back out through the capsule to the medial aspect of the knee (i.e., the so-called “outside-in” technique). The aforementioned tethering issues relate to more recent concerns about fixating suture over the knee capsule and thereby “tethering” the meniscus to the knee capsule, since evidence suggests that such tethering of the meniscus to the knee capsule may interfere with the normal biomechanics of the meniscus (e.g., load and force distribution, etc.).
As recognition of the importance of the meniscus grew in the late 1980's, new methods of meniscus repair were developed. These new methods focused on improving execution of the procedure in order to make it easier, simpler and faster to accomplish. The new gold standard approach became the so-called “all-inside” technique. The all-inside technique is intended to not violate the knee capsule or require any incisions on the posterior/medial aspects of the knee (i.e., such as is required with the inside-out and outside-in suturing techniques discussed above). With the all-inside technique, the entire repair—both approximation and fixation—is performed intra-articularly.
The first all-inside repair devices were tack-like implants that were inserted through a standard arthroscopic portal and then forcefully pushed through the meniscus, crossing through the tear, thereby closing and fixing the tear without the use of suture. These tack-like implants were formed out of biomaterials such as PLA, PLLA or PGA that were expected to biodegrade over time. However, these materials are quite hard when first inserted and, in use, were found to degrade or bioabsorb much more slowly than anticipated. Clinical use and follow-up have demonstrated the inherent risks associated with the use of tack-like implants within the knee joint, as numerous published studies have reported device failure which can lead to tear reformation, loose implants within the knee joint and articular cartilage damage. Furthermore, it can be challenging for the surgeon to adequately address various tear shapes and sizes using these tack-like implants.
As a result, attention has returned to suture-based repairs, with a new focus on performing a suture-based repair using an all-inside technique. There are several recent systems that seek to accomplish this goal. However, none of these systems have been found to be completely satisfactory.
Thus, there is a need for a new and improved method and apparatus for meniscal repair.